1. Field of the Invention
The present invention relates to a cooling apparatus of a vehicle. More particularly, the present invention relates to a cooling apparatus including an engine cooling system and a second cooling system which is to be kept at a temperature lower than that of the engine cooling system and is improved in a cooling ability thereof.
2. Description of Related Art
A cooling apparatus of a hybrid vehicle includes an engine cooling system and a hybrid component cooling system (a second cooling system).
In order to keep the temperature of cooling water of the hybrid component cooling system equal to or lower than an allowable temperature, as illustrated in FIG. 7, the cooling system of the hybrid vehicle of a first comparison is provided with an engine cooling radiator 31 (a cooling portion of the engine cooling system) and a hybrid component cooling radiator 32 (a cooling portion of the second cooling system) which are disposed separately from each other. The hybrid component cooling radiator 32 is disposed in front of an air conditioner condenser 33 and the engine cooling radiator 31 is disposed in the rear of the air conditioner condenser 33.
The reason for this arrangement is as follows: As will be understood from the following heat balance equation:Q=KF(Tw−Ta)where, Q: heat amount removed from water to air
KF: heat transmittance constant of the radiator
Tw: cooling water temperature
Ta: wind temperature,
there is a relatively large air-water temperature difference of about 50° C. (+10°C.–+15° C.) in the engine cooling system, while in the hybrid component cooling system, an air-water temperature difference is relatively small and insufficient to keep the hybrid component cooling system at a temperature lower than the allowable temperature thereof, in case where the radiator of the hybrid component cooling system is disposed in the rear of the air conditioner condenser, because the wind temperature rises by +10° C.–+15° C. when the wind passes through the air conditioner condenser. To obtain a relatively large air-water temperature difference at the radiator of the hybrid component cooling system, the radiator of the hybrid component cooling system is disposed in front of the air conditioner condenser.
However, the arrangement of FIG. 7 has the following problems:    (a) A number of the radiators is increased to “2”. When counting the air conditioner condenser as a radiator, the number of the radiators is “3”. The increase in the number of the radiators is accompanied by an increase in cost.    (b) A crushable zone for front collision of a vehicle is decreased by the space occupied by the radiator of the hybrid component cooling system, and a damageability of the vehicle is lowered.    (c) Due to a temperature increase of the wind flowing to the air conditioner condenser, an electric power consumed in driving the air conditioner compressor is increased, and in turn, an actual fuel economy is lowered.
To suppress the above-described problems, another cooling apparatus of a second comparison illustrated in FIG. 8 can be conceived. In the apparatus, the radiator 32 of the hybrid component cooling system is shifted to the rear of the air conditioner condenser 33 such that the shifted radiator 32 and the air conditioner condenser 33 are overlapped when viewed in a front-to-rear direction of the vehicle, and the radiator 32 of the hybrid component cooling system and the radiator 31 of the engine cooling system are integrated into a single composite radiator 34 where the radiators 31 and 32 are partitioned from each other. The composite radiator is a multi-function cooling module having an engine cooling function and a hybrid component cooling function.
However, the radiator of FIG. 8 still has the following problem: Since the radiator 32 of the hybrid component cooling system (the second cooling system) is disposed in the rear of air conditioner condenser 33, a temperature of the wind having passed through the air conditioner condenser 33 rises by +10° C.–+20° C. As a result, it is difficult to obtain a relatively large air-water temperature difference sufficient to keep the temperature of the cooling water of the second cooling system at a temperature lower than the allowable temperature. This is accompanied by a decrease in the cooling ability of the second cooling system or, if the cooling ability is maintained, an increase in a size of the radiator 12 of the second cooling system.